Treatment of still residue



Patented Nov. 1, 1938 UNITED STATES TREATMENT OF STILL RESIDUE Frank W. Corkcry, Clairton, Pa., assignor to Pennsylvania Industrial Chemical Corporation, a corporation of Pennsylvania No Drawing. Application July 2, 1936, Serial No. 88,591. Renewed March 19, 1938 4 Claims.

This invention relates to the treatment of still residue by oxidation, and more particularly to the treatment of the still residue in preparation for oxidation. 1

5 'The still residue with Which I deal isa still residue remaining from the treatment of cokeoven light oil. This still residue contains polymers of resin-forming bodies in various stages of polymerization, heavy monomers, naphthalene, and varying percentages of solvents and sulphonates. It is a dark, viscous, oily substance deficient in drying qualities, and. of itself possessing but little utility in the arts. In my co -pending applications Serial No. 53,213, filed mi December 6, 1935, Serial No. 54,852, filed December 17, 1935, and Serial No. 62,045, filed February 3, 1936, I have respectively disclosed methods of producing useful products by oxidizing the total content of still residue by itself to form 0 an elastic body, of oxidizing the still residue in association with a non-mineral pitch, and of oxidizing the still residue in association with a drying oil.

It should be understood that still residue as 525 commercially available is not uniform in its content and qualities. The light oil from which the still residue has its immediate derivation is chiefly obtained from the gases coming ofi during the lay-product coking of coal. As this op- 30 eration is performed usually at plants directly associated with large steel companies, and as these companies follow variant procedure in treating and fractionating the by-product yield, still residue from some sources cannot be treated identically with that from other sources. Thus many still residues have a content of sulphonates so low that no treatment for their removal is necessary. Other still residues contain sulpho-nates in such proportions that it is of im- 40 portance to remove them prior to oxidizing the still residue. It is with still residue of thislatter type that the initial stages of my preparatory treatment are concerned.

In preparation of still residues containing a 45 large content of sulphonates and/or sulphates resultant from the purification of the light oil and light oil fractions, to obtain from them a clear oxidized product free from objectionable odor, I make specific adaptation of the solvent 50 separation principle. In so doing, I commingle the still residue with a suitable petroleum distillate, such as petroleum naphtha, mineral spirits, kerosene ligroin, gasoline, and the like, in which the sulphonates and sulphates are relatively in- ,55 soluble. Upon commingling the petroleum distillate with the still residue, Without heating,

there occurs a precipitation of the sulphonates and sulphates from the solution. I have 'iound that any substantial quantity of the petroleum distillate causes precipitation of sulphonates and 5 sulphates, but have also found that, if the initial content of sulphonates or sulphates is substantial, adequate removal of them is not-efiected unless the volume of petroleum distillateiis at least equal to the volume of thestill residue. 7 10 To describe my preferred conditions, I have found that within the ratio of from 2 to 5 volumes of petroleum distillate to each volumeof still residue precipitation of sulphonates and/or sulphates present in any quantity in the still residue is substantially complete. If the petroleum, distillate approaches in quantity 5 volumes of the petroleum distillate to each volumeof the still residue, the conditions being otherwise suitable, separation of the precipitate from the solu- 52 tion may be efiected merely by permitting the suspension to settle. By commingling the still residue with petroleum distillate to form a solution therewith at normal room'temperature, the precipitate is of a granular, readily separable nature. At substantially higher temperatures the precipitate does not form in this granular condition. It' is desirable,. therefore, in cases where the solution is made under extraordinarily high atmospheric conditions, and cases in which the still residue has become spontaneously heated, to cool the solution to a temperature not exceeding 80 F.

The precipitate comprises the sulphonates and sulphates initially present in the still residue, and may have associated with them traces of other foreign matter insoluble in the petroleum distillate. If a mere settling is inadequate to effect separation of the precipitate from the solution of still residue in the petroleum distillate, 40

separation of the solution and precipitate is effected by filtration. After separation of the precipitate, the still residue solution is agitated with a small quantity of sodium hypochlorite followed by a sodium hydroxide wash, and water washing. These agents cooperate'in rendering removable from thesolution impurities which are soluble in the petroleum distillate; thus purifying the solution generally, and eliminating the disagreeable. sweetish odor which is a characteristic 'of untreated still residue.

I then introduce into the solution bleaching clay of any of the well known sorts, desirably in a weight of from 2 .to 5 per cent. the Weight of the solution, agitate it in the solution, and filter it out. The clay, as filtered from the solution, carries with it some of the color-forming bodies of the still residue; leaving the solution improved in color as well as odor, and containing a lessened content of impurities.

Following the clay treatment, the still. residue is recovered from solution by distilling overv the petroleum'distillate ln-which lt is dissolved. This distillation desirably is carried to a temperature of approximately 425 F. under vacuum, in order wholly to remove naphthalene and the solvent content of the still residue. It' is possible to utilize straight distillation. up to a temperature of from 390 F. to 400 F.. distilling'iundervacuum only in the high temperature range.v

Still residueso treated is in good condition for oxidation into the form of a residual gum-by blowing air or undiluted oxygen therethrough, or.

' for a similar oxidizingtreatment in admixture with a drying oil such as linseed oil, fish oil, or the like. It 'may alsobe oxidized as it'is in admixture-with a non-mineral pitch, such'as cottonseed pitch, stearin pitch, and thelike. I

have discovered, however, that 'compatability of the still 'residue'and the pitch as oxidized togeth- 7 er may bebroughtcloser to the absolute, and the high stage" of imixture of still residue and pitch.

qualities. of the product may otherwise be im-' proved by removing 'a portion oi such oily content of the purified still residue as is not formed ofthe'hi'gher polymer'content of the still residue.

'Thisis for the-reason'that non-mineral pitch possesses itself, when oxidized, considerableelasticity; and. also for the reason that (unlike the drying. oils) a degree of inoompatability between V thelstill residue and the pitch develops when a oxidation has been reached in a 1 .Taking then'a' topped still residue freed of sulphor ates and otherimpurities, and stripped of a. portion of its'lower' boiling end, it' is commingled with a pitch of non-mineral origin in a vessel equipped with heating means and with means for forcing gases therethrough. As a desirable procedure, the temperature of the pitch is raised in the treating vesselto the melting- 'pointiof the'pitch before the still residueis in- L-troduced and mixed with the pitch, but in any event the temperature of the mixture is ra-ised to atleastthe meltlng-point of the'pitch before blowing is begun.

During arelatively extendedblowing period,

heat is supplied to the vessel adequate to maintainthe mixture at, such temperature that itis in'con'dition suitable for the dispersion of oxygen therethrough. As oxidation proceeds, it is necessary progressively to. increase the temperature of the mixture in order that itmay sufil- -.ciently *be liquid for the oxygen' dispersion. I

havefound a temperatureprogressively raised within the range of 160 F. to 300 F. suitable for V the oxidizing treatment.' When, as is most convenient, air is the source of oxygen, blowing desirably is' continued for from 3 to fifdays. When pure, or relatively p'ure, oxygen is used an ap-*.

propriately'shortened treating period suffices to bring the mixture to an equal stage 'of oxida-" tion."'. V V

The resultant productis an' elastic mass, which @isclear and of light colonand which is soluble in the aromatic hydrocarbon solvents. Depending upon the proportion of pitch to still residue,

and the stage to which oxidation is carried, it is soluble in the varying percentage mixtures of aromatic solvents. I have found a composite of equal volumes of still'residue and non-mineral.

'ing delicate tints, and is highly elastic.

' desired.

. ticity of the product may be obtained. The composite product is also useful for the waterproofing'of paper, fabric, and other normally absorb- ;ent materials.

The relative proportionsv of the still residue and the non-mineral pitch in the composite may be varied within relatively wide limits from equality one with the other without substantial. loss in any of the qualities of elasticity and solubility of the product, and without impairing the compatibility of the components of the composite. It may be noted that the composite product remains clear and bright throughout a' pulling test, thus indicating substantially complete removal of sulphonates.

sirably remove to 75% of the, lighter oil end of the still residue as it exists after purifica- 5 tion, and after the removal of solvents and naphthalene. The extent to which the still residue is advantageouslystripped depends upon e In preparation for mixture and blowing, I de-' the proportional quantity of the 'still residue ineluded in the composite, and the stage'of oxidation to which it is carried. 'The elasticity of "the-product, or, as otherwise expressed, the penetrationof the product, depends upon the content-of the oily lower polymers remaining in the still residue. In no event, however, do I find'it desirable wholly to deprive the still residue of its .content of lower polymers.

I When the preparation of a still residue of the specified type (a still residue from the treatment" of coke-oven light oil) involves a purification such as-that outlined above, the removal of a portion of the lower polymer oils may follow as an incident to distilling off the mineral spirits used in purification and the initial 501- vent. and naphthalene content of the still residue. In such case distillation under vacuum at a temperature at and above 425 F. is continued until the still residue has been stripped of the In preparing a still residue which need not be subjected to the preliminary purification, it may nonetheless be stripped of a portion of its oily,

lower boiling content in similar manner, as a step preparatory to its oxidation; While it has 7, been stated above that purification need not be practiced upon some still residues, it. may be dedesired quantity of its 'oily, lower boiling end.

sirable' to remove sulphonates even from stilt;

residues containing a relatively small proportion of them when a product. of particular'purity'is The removal of. a portion of the lower boiling,

oily constituentsyof the still residue is, as'stated above, generally'desirable only in preparation "'oflthe still residue for oxidation in association with pitch to 'give'a pitchy composite. In rare instances, it maybe practiced to modify the procedure in producing a residual gum disclosed in my co-pending application Serial No. 53,213,

reference to which has been made above. It is appropriate when for some purpose aproduct of decreased-elasticity and penetration may be desired. In such event the still residue, deprived of a portion of its oily, lower boiling content, is subjected by itself. to oxidation. The method of oxidization is similar to blowing air or oxygen in less dilute condition through the stripped still residue while supplying to the still residue heat adequate to maintain it in condition suitable f r the oxygen dispersion. As compared with the procedure disclosed in detail in my application Serial No. 53,213, the period of treatment may be shortened because of the reduced lower boiling content of the still residue, 3 or 4 days of blowing treatment with air being adequate for the production of a gum which is solid at temperatures higher than normal room temperature. The removal of a portion of the oily, lowerboiling content prior to oxidation may be practiced on the still residue whether or not it has been subjected to a. purifying treatment.

It may be explained that the absence of sulphonates in a product such as the oxidized composite pitch, oxidized composite of still residue and drying oil, or oxidized still residue alone substantially improves the solubility of the resultant product, and also to some extent improves its waterproofing qualities.

In connection specifically with the oxidized composite of still residue and non-mineral pitch, the removal of a portion of the oily lower polymers of the still residue serves substantially to improve the compatibility of the components and the solubility of the composite when carried to a relatively high stage of oxidation at which it acquires a melting-point of Fqand higher. In the modified pitch this advantage accompanies the advantage of avoiding an elasticity so high as to be undesirable for certain uses, such as its use in tile manufacture.

I claim as my invention:

1. The herein described method of oxidizing liquid aromatic still residue from the treatment of coke-oven light oil initially containing sulphonates and like impurities. in association with non-mineral pitch to produce an oxidized pitchy composite of light color and transparent in a film the components of which are in a condition of. approximately absolute compatibility, which comprises precipitating the sulphonates and like impurities of the still residue by solvent separation in a petroleum distillate, separating out the precipitate, by distillation separating from the still residue the petroleum distillate and the lower boiling end of the still residue including a portion of the oily lower polymers thereof; and oxidizing in admixture the still residue so purified and prepared with a pitch of non-mineral origin by oxygen dispersion through a mixture of the still residue and pitch while supplying to the mixture heat adequate to maintain it at a progressively increased liquefying temperature.

2. The herein described method of oxidizing liquid aromatic still residue from the treatment of coke-oven light oil in association with nonmineral pitch to produce an oxidized pitchy composite of light color and transparent in a film the components of which are in a condition of approximately absolute compatibility, which comprises removing a portion and less than all of the oily lower polymers of the still residue; and oxidizing in admixture the still residue so prepared and pitch of non-mineral origin by oxygen dispersion through a mixture of the still residue and pitch while supplying to the mixture heat adequate to maintain it at a progressively increased liquefying temperature.

3. The herein described method of. oxidizing liquid aromatic still residue from the treatment of coke-oven light oil initially containing sulphonates and like impurities in association with non-mineral pitch to produce an oxidized pitchy composite of light color and transparent in a film, the components of which are in a condition of approximately absolute compatibility, which comprises freeing the raw still residue of sulphonates and like impurities, removing from the still residue which has been freed of sulphonates a portion of the lower oily polymers thereof, and oxidizing in admixture the still residue so purified and prepared with a pitch of non-mineral origin by oxygen dispersion through a mixture of still residue and pitch while supplying to the mixture heat adequate to maintain it at a progressively increased liquefying temperature.

4. The herein described method of oxidizing liquid aromatic still residue from the treatment of coke-oven light oil initally containing sulphonates and like impurities in association with non-mineral pitch to produce an oxidized pitchy composite of light color and transparent in a film, the components of. which are in a condition of approximately absolute compatibility, which comprises removing the sulphonates and like impurities from the raw still residue, and oxidizing in admixture the still residue purified by removal of sulphonates and pitch of nonmineral origin by oxygen dispersion through a mixture of the still residue and pitch while supplying to the mixture heat adequate to maintain it at a progressively increased liquefying temperature.

FRANK W. CORKERY. 

